Identification of Some Macromolecules
Introduction
The goal of this experiment is to react certain solutions using different tests, which consist of the Iodine test, used to determine the presence of starch and glycogen through colour change (Morris, 1946), Benedict’s test, used for determining the presence of sugars (Benedict, 1908), and the Biuret Test, used for determining the presence of proteins (Gornall, Bardawill & David, 1948), to identify certain macromolecules, a large, organic molecule, that exist within these solutions.
Materials and Methods
All of the procedures were carried out as outlined in Lab 2: Identification of Some Macromolecules, BIOL 130L lab manual, pages 27- 30 (Department of Biology, 2019). The unknown solution used in beaker #12 in this experiment was solution #61.
Results Legend: (+) Positive Results after the test (-) Negative Results after the test
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Iodine test Benedict’s Test Biuret Test Initial Colour yellowish tint blue tint blue tint |
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#1 colourless/transparent yellow (-) light orange/red (+) light blue (-) transparent opaque transparent #2 colourless/transparent yellow (-) blue (-) light blue (-) transparent transparent transparent #3 colourless/transparent yellow (-) orange/red (+) light blue (-) transparent opaque transparent #4 slight yellow tint/transparent yellow (-) brownish green (+) light turqoise (-) transparent opaque transparent #5 colourless/transparent yellow (-) blue (-) light blue (-) transparent transparent transparent #6 colourless/transparent yellow (-) light orange (+) light blue (-) transparent opaque transparent #7 colourless/transparent brownish/red (+) blue (-) light blue (-) opaque transparent transparent #8 colourless/transparent black/blue (+) blue (-) light blue (-) opaque transparent transparent #9 murky white with bubbles yellow (-) blue (-) lavender purple (+) translucent transparent transparent transparent #10 light yellowish-brown yellow (-) mustard yellow (+) light green (-) tranparent transparent precipitate formed, opaque transparent #11 colourless/transparent yellow (-) blue (-) light blue (-) transparent transparent transparent #12 colourless/transparent black/blue (+) blue (-) light blue (-) opaque transparent transparent |
Discussion
When referring to the results and the introduction, we can come to conclusions about the presence of specific macromolecules existing within certain tested solutions in this experiment. All of the data matched the expected values and results except for two tested solutions, #4, the 5% honey solution and #10, the beer, as there were unexpected colouration differences from the expected results with the honey solution and the beer but that was caused by the original base colour of the solution. Overall, there weren’t many errors within the techniques and data since most of the procedure is quite straightforward and didn’t demand anything too challenging, and if not the majority, all of the data collected is qualitative and approximate. Starch contents turn blue when reacted with iodine (Holló & Szejtli, 1957), and the only solution tested positive for starch was solution #8, the 1% starch solution. This being the only matching reaction with our unknown solution, we can conclude that the unknown solution in our test was a starch solution as well.
References
- Benedict, S. R. (1908). A REAGENT FOR THE DETECTION OF REDUCING SUGARS. Sheffield Laboratory of Physiological Chemistry, Yale University
- Department of Biology. (2019). Introductory cell biology laboratory. Waterloo, Canada: University of Waterloo Print + Retail Solutions
- Gornall, A. G., Bardawill, C. J., & David, M. M. (1948). DETERMINATION OF SERUM PROTEINS BY MEANS OF THE BIURET REACTION. Department of Pathological Chemistry, University of Toronto, Toronto, Canada
- Holló, J., & Szejtli J. (1957) THE MECHANISM OF STARCH-IODINE REACTION. Institute of Agricultural Chemical Technology, University of Technical Sciences, Budapest.
- Morris, D. L. (1946). COLORIMETRIC DETERMINATION OF GLYCOGEN DISADVANTAGES OF THE IODINE METHOD. Department of Nutritional Research, Mead Johnson and Company, Evansville, Indiana
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